Do Zombies Dream of Undead Sheep?: A Neuroscientific View of the Zombie Brain

By Timothy Verstynen and Bradley Voytek

A look at the true nature of the zombie brain

Even if you've never seen a zombie movie or television show, you could identify an undead ghoul if you saw one. With their endless wandering, lumbering gait, insatiable hunger, antisocial behavior, and apparently memory-less existence, zombies are the walking nightmares of our deepest fears. What do these characteristic behaviors reveal about the inner workings of the zombie mind? Could we diagnose zombism as a neurological condition by studying their behavior? In Do Zombies Dream of Undead Sheep?, neuroscientists and zombie enthusiasts Timothy Verstynen and Bradley Voytek apply their neuro-know-how to dissect the puzzle of what has happened to the zombie brain to make the undead act differently than their human prey.

Combining tongue-in-cheek analysis with modern neuroscientific principles, Verstynen and Voytek show how zombism can be understood in terms of current knowledge regarding how the brain works. In each chapter, the authors draw on zombie popular culture and identify a characteristic zombie behavior that can be explained using neuroanatomy, neurophysiology, and brain-behavior relationships. Through this exploration they shed light on fundamental neuroscientific questions such as: How does the brain function during sleeping and waking? What neural systems control movement? What is the nature of sensory perception?

Walking an ingenious line between seriousness and satire, Do Zombies Dream of Undead Sheep? leverages the popularity of zombie culture in order to give readers a solid foundation in neuroscience.

• Language: English
• Publisher: Princeton University Press
• Release date: Sep 22, 2014
• ISBN: 9781400851928

Book preview

DO ZOMBIES DREAM OF UNDEAD SHEEP?

DO ZOMBIES DREAM OF UNDEAD SHEEP?

A NEUROSCIENTIFIC VIEW OF THE ZOMBIE BRAIN

TIMOTHY VERSTYNEN & BRADLEY VOYTEK

PRINCETON UNIVERSITY PRESS

PRINCETON AND OXFORD

Copyright © 2014 by Princeton University Press

Published by Princeton University Press, 41 William Street, Princeton, New Jersey 08540

In the United Kingdom: Princeton University Press, 6 Oxford Street, Woodstock, Oxfordshire OX20 1TR

press.princeton.edu

Cover design and interior by Jessica Massabrook

Third printing, first paperback printing, 2016

Paperback ISBN: 978-0-691-17315-3

The Library of Congress has cataloged the cloth edition as follows:

Verstynen, Timothy, 1978–

Do zombies dream of undead sheep? : a neuroscientific view of the zombie brain / Timothy Verstynen & Bradley Voytek.

   pages cm

Includes bibliographical references and index.

ISBN 978–0-691–15728–3 (hardback)

1. Neurosciences.    2. Zombies.    3. Brain.    I. Voytek, Bradley,

1981–   II. Title.

QP355.2.V47 2014

001.944—dc23                         2014011128

British Library Cataloging-in-Publication Data is available

This book has been composed in Avenir LT Std & Adobe Caslon Pro

Printed on acid-free paper. ∞

Printed in the United States of America

10 9 8 7 6 5 4 3

CONTENTS

FIGURES

PRELUDE

SACRIFICES NOT MADE IN VAIN

This book is about science. It is about exploring the essence of what it means to be a thinking human being. Unfortunately neuroscience is a science built partly on tragedy.

Much of our understanding of the human brain comes from studying instances where an injury or malady has afflicted the brain of a living person. These individuals are not just anonymous people hidden behind initials in the medical literature, they are our loved ones. They are our parents, our spouses, our siblings, our children, and our best friends. Yet as a result of some misfortune their lives are permanently altered because damage to their central nervous system has caused them to behave, think, or perceive differently.

By studying the relationship between these injuries and subsequent changes in behavior, we can gain invaluable insights into how our brains actually work. Our evolving understanding of the human brain not only furthers basic science, but also lays the necessary foundation for the development of new therapies and (hopefully) cures. As a field we are constantly striving to squeeze every ounce of knowledge that we can from these very personal tragedies, in order to improve the world, one patient at a time.

While much of this book appears to be about zombies, it is in fact an ode to the lessons that are learned from such personal tragedies. It is an ode to the scientists who took the time to get to know their patients well enough to understand the complex ailments that impacted their everyday lives. It is an ode to those who, often by no fault of their own, suffered from a malady and yet endured to allow a stranger in a white coat to ask why and how.

INTRODUCTION

Having picked this book off the shelf, you’re probably asking yourself, How could there be a neuroscience of zombies? While yes, zombies do have brains (you have to destroy their brains in order kill them, or so the myth goes), we would be hard pressed to make a case that zombie neuroscience qualifies as its own field of study. Neuroscience—the study of the brain, particularly its relationship to behavior and cognition—already has its fair share of perhaps silly and fantastical specialty subfields; why add to the list?

Well, did you know that we neuroscientists have the answer to every thing? Regular readers of the Opinion page of the New York Times or other popular media outlets will already know that neuroscience can explain why you are in love with your iPhone, why lying to your kids about Santa is a neurologically sound form of parenting, and why inducing a coma leads to proof of heaven. You see, by filtering all of human existence through our very muddy lens we can answer all of life’s questions. By our estimates, an fMRI study explaining the meaning of life should be coming out by sometime early 2015 (hint: it involves 42 brain regions). We hate to break it to our colleagues in the fields of philosophy, religion, and physics, but thanks to a few fancy brain imaging machines and a couple of decades of pretty hard thinking about stuff, we neuroscientists now can understand everything, so they’ll probably need to seek employment elsewhere.

If neuroscience is the panacea and explanation for everything else, why not the zombie apocalypse? There’s a market for that, right?

Let’s return to the book you are holding in your hands. It all started one day in the summer of 2010 with a phone call from Matt Mogk, the head of the Zombie Research Society and author of That’s Not Your Mommy Anymore and Everything You Ever Wanted to Know about Zombies. Matt had seen a YouTube video of a lecture Brad had given wherein Brad mentioned how he was raised on a diet of Sega and Marvel Comics. Matt wanted to know if, given Brad’s double-barreled love of comic culture and brains, he would be up for exploring the nature of the zombie brain. Brad thought, Of course … and I know just who to ask along on this crazy ride….

It’s been all downhill for us both ever since.

We (Tim and Brad) met while working on our PhDs at the University of California, Berkeley. We briefly collaborated on a noninvasive brain stimulation project that, like many scientific experiments, led absolutely nowhere, but in the process we discovered a mutual love for zombie movies. So in addition to doing real science together, we branched out into the ridiculous world of zombies. We hope you enjoy the ridiculous, and we hope that you don’t hold our real science against us.

In all seriousness, this zombie stuff has been a lot of fun. We’re both geeks who also happen to be big advocates of science outreach and communication. This is a rare opportunity to combine our geek science and non-science sides. Brad has been going to the San Diego Comic Convention annually for the last decade, and off and on since he was a pimply young teen twenty years ago. Never in his life did he think that his scientific career would lend itself to speaking in front of a crowd of several hundred comic book geeks at that convention (in the same room, in fact, where he gave a real neuroscience lecture to a room of far fewer neuroscientists at the annual Society for Neuroscience Conference).Tim has been addicted to zombie movies since he first saw back-to-back features of Night of the Comet (dir. Thom Eberhardt; 1984) and Return of the Living Dead (dir. Dan O’Bannon; 1985) as a teenager. It might be said that Tarman¹ brought Tim’s attention to brains in the first place.

In the years that we’ve been talking about the biological basis of zombie behavior, we’ve been overwhelmed by how much people have gotten into it with us. When you have people coming up to you saying things like I’m a grown man with a family and a career and you guys made me want to become a neuroscientist! or I accidentally started liking science stuff thanks to you! you know you’re onto something. As scientists we spend so much time working on problems that feel disconnected from the public that it’s great to know we’re finally doing something that resonates with people. Especially if it’s goofy.

No, neuroscientists have no idea (biologically) what love is, or where it is stored in the brain. Neuroscience can’t prove that you love your iPhone (that was a real New York Times opinion piece, by the way²). We can’t read your minds (yet) or cure Alzheimer’s disease (yet).

While neuroscience can’t do those things, we hope that two somewhat ludicrous neuroscientists, and a horde of zombies, can make you accidentally learn something, and that in reading this book you might share our sense of the wonder we experience in doing the work we love.

There’s no doubt that zombies are hot right now. There’s been a lot of discussion as to why, as several of us (Brad, Max Brooks, Matt Mogk, and a few other zombie experts) discussed at a panel at Comic-Con in San Diego in 2011 (Comic-Con is an annual gathering of over 100,000 nerds of all flavors and colors). Our favorite explanation for the general surge in zombie popularity is that the world is becoming an increasingly complex place, with new modes of social interaction and communication, increased globalization, social change, unprecedented technological advances, prosperity mixed with uncertainty, and so on. The great thing about the zombie genre in TV, video games, and movies is that it’s more or less a blank slate upon which a writer can project any number of big, unfathomable societal and psychological fears or concerns.

Genetic modification? Zombies. Atomic weapons and radiation? Zombies. Class warfare? Zombies. Racism? Zombies. Existential crisis and uncertainty of the self or free-will? Zombies. Biological experimentation? Zombies. Space exploration? Zombies. Runaway consumerism? Zombies. Pointless violence? Zombies. Death? Zombies.

Max Brooks once said in an interview with CNN, You can’t shoot the financial meltdown in the head—you can do that with a zombie…. All the other problems are too big. As much as Al Gore tries, you can’t picture global warming. You can’t picture the meltdown of our financial institutions. But you can picture a slouching zombie coming down the street.³

It is hard to ignore the runaway popularity of the zombie phenomenon. In 2002, 28 Days Later was released, providing a fresh take on zombie film that helped revitalize the genre. That same year, Resident Evil was remastered and rereleased for the Nintendo GameCube to huge critical acclaim.⁴ The following year, in 2003, Max Brooks wrote the very popular Zombie Survival Guide that kicked the whole zombie literature genre into high gear. Then, in 2004, Shaun of the Dead showed that the zombie genre could also be funny, paving the way for films such as Fido (2006), Zombieland (2009), and Warm Bodies (2013). In the 1980s there had been brief bouts of funny zombie movies, for example Night of the Comet (1984) and Return of the Living Dead (1985), but none of them hit the level of popularity of the modern zombie-comedy.

Here, in this book, we want to leverage this more comical or farcical take on zombies. The goal of the rest of the book is to use zombies to provide an entertaining platform for understanding (and sometimes making fun of) our field of cognitive neuroscience, and along the way teach the reader about the history of neurological science and about properties of the brain itself. We are not going to use zombies as a metaphor for social ills. Instead we are going to try to understand the zombie by taking a careful look at the range of its behavioral disorders, peeking into the mythical organ that gives rise to all zombie behavior: the zombie brain.

As the lonely graduate student uttered at the beginning of 28 Days Later, before being torn apart by a zombie ape, In order to cure you must first understand.

So here we are, trying to understand. What follows is a collection of neuroscientific facts, historical footnotes, personal anecdotes, and a ton of zombie and pop culture references. In particular, we’ll be making a lot of references to scenes in classic and neo-classic zombie film and literature. Specifically, you will hear plot points from:

Night of the Living Dead (dir. George Romero; 1968)

Dawn of the Dead (dir. George Romero; 1978)

Return of the Living Dead (dir. Dan O’Bannon; 1985)

The Serpent and the Rainbow (book, Wade Davis; 1985)

Evil Dead 2 (dir. Sam Raimi; 1987)

28 Days Later (dir. Danny Boyle; 2002)

Shaun of the Dead (film, dir. Edgar Wright; 2004)

Land of the Dead (dir. George Romero; 2005)

Fido (dir. Andrew Currie; 2006)

Zombieland (dir. Ruben Fleischer; 2009)

Feed (book, Mira Grant; 2010)

The Walking Dead (TV series, 2010–)

Warm Bodies (dir. Jonathan Levine; 2013)

World War Z (book, Max Brooks; 2006; film, dir. Marc Forster; 2013)

In our descriptions throughout, there will be spoilers. Consider yourself warned.

Actually, we take that back. We recommend you go out right now to watch all of these movies and read all of these books. Go ahead … we’ll wait.

Are you back? Good. Expect a lot of spoilers ahead!

This work is a mixture of material we have put together from previous projects in other mediums; you may recognize some of our stories from our blogs or talks, but we’ve collected all the little tidbits here in one nice, concise reference book for your own zombie studies.

Now, fellow scientists of the undead … on to the realm of zombie brains!!!

---

¹ Tarman is perhaps the most recognizable zombie in popular culture, single-handedly binding brains and zombies into the same sentence.

² Martin Lindstrom, You Love Your iPhone. Literally, New York Times Sept. 30, 2011 (http://www.nytimes.com/2011/10/01/opinion/you-love-your-iphone-literally.html?_r=0).

³ http://www.cnn.com/2009/SHOWBIZ/10/02/zombie.love/index.html?iref=24hours.

⁴ IGN’s tagline says it all: The prettiest, most atmospheric and all-around scariest game we’ve ever played: http://cube.ign.com/articles/358/358101p1.html.

GRAY’S (UNDEAD) ANATOMY

With savages, the weak in body or mind are soon eliminated; and those that survive commonly exhibit a vigorous state of health.

—Charles Darwin, The Descent of Man

You are about to read a book about the zombie brain. Just think about that for a minute. Let the thought really soak in. Reflect on the decisions you’ve made in your life that led you to this point.

Now let’s get a bit meta for a moment and think about all of that thinking and reflecting you just did. First, you read some words that we wrote via a semi-creative process. You understood those words and they changed your behavior. You reflected on your life by some internal memory recollection process. Perhaps you even thought about what decisions led us to the point of writing this book in the first place.

This amalgamation of thoughts, memories, and emotions that you just experienced, and will keep experiencing while reading this book, are all the result of a never-ending symphony of electrochemical processes in your brain. Each step of thinking that you just performed, from seeing the printed letters on the page to following the linguistic requests that we asked of you by pulling up the memories of the past, is performed by little networks of neurons distributed throughout that gray matter sandwiched inside your skull.

As neuroscientists, the fact that we can do all of that thinking is completely amazing. But what if you couldn’t do any of that? Or what if you could do some of those things, but could feel no emotions about them? Or what if you could feel emotion, but had no memory?

The study of neuroscience isn’t just about tissues and neurons and signals; it also has strong philosophical, computational, and psychological roots. It is a very difficult, sometimes wonderful, but often frustrating, problem.

Which is how we got to this point. As we said in the introduction, this is a book by a couple of scientists who also happen to be zombie movie nerds.

Our goal for this little thought experiment is to understand what has happened to the walking dead that has changed them from normal human beings to so-called mindless walking corpses.¹ To do this we need to understand how the brain gives rise to behavior, in both humans and zombies. Which means we first have to understand exactly what the brain is.

But before we can get knee-deep in zombie gray matter, let us take a step back and look at the little three-pound piece of tissue sandwiched between your ears.

NEUROSCIENCE WITHOUT BRAIN SCANNERS

In this chapter and those that follow, we will attempt to link features of zombie behaviors to the various parts of the brain by adopting a classical forensic neurology approach.

What do we mean by this?

Classic neurology was the original scientific method for studying the brain before we had big machines to take pictures inside the living skull. Neurology is mainly focused on understanding why certain things go wrong in the brain to cause a patient’s symptoms, but along the way it has learned a lot about how the healthy brain works too. When neurology began in the mid-1800s, doctors had to deduce how the brain works by simply observing the behaviors of people and animals. This is a delicate art that involves making deductions about the brain by carefully detailing your subject’s behavior. But it didn’t just start with the advent of neurology in the nineteenth century. In fact, this form of investigation has been going on for centuries.

Indeed, while we tend to think of neuroscience (the empirical study of the healthy brain, as opposed to neurology, which is the medical branch dealing with brain disorders) as a modern scientific endeavor, some of the first experimental research linking the brain and nerves to behavior came from experiments and demonstrations by the Roman physician Claudius Galen, sometime between 150 and 190 CE.

Keep in mind that we’re talking about a time nearly 2000 years before brain imaging, well before Dr. House could just send his patients to an MRI to see how healthy their brains were. Back then, physicians and scientists had to do a lot with very little information. They had to get creative. This meant that they tried a lot of things; some worked and some didn’t. But sometimes they learned something new that would add just a bit more to what little was known about the brain.

For example, in a famous experiment on a living pig, Galen was trying to trace out the nerves involved in breath control when he accidentally cut the recurrent laryngeal nerve, which controls the muscles of the larynx (aka the vocal cords). The live pig immediately stopped squealing, but was still moving and breathing. Thus, like many great scientific discoveries, he found out how vocal cords are controlled, purely by accident.

Galen was also the doctor to the Roman gladiators, a group of folks that were highly susceptible to injury. In the process of treating these often brutally injured men, he observed how cuts to the spinal cord affected behavior, notably causing paralysis below the level of the cut. He continued this work by experimenting on animals and noticed that cutting the spinal cord very high up, in the brainstem, would kill the animal. This observation gave us the first glimpse into how our limbs are controlled by different outputs along the spine.

Unfortunately, after Galen there was a long hiatus in the development of our knowledge of the brain, until the Enlightenment brought a resurgence in the idea of the scientific method. In the early 1800s, Marie Jean Pierre Flourens conducted experiments similar to those done by Galen, but mainly on rabbits and pigeons. He removed different parts of their brains and observed their behaviors in order to understand how different brain areas related to behavior. He found that depending on the specific region that was removed, the animals lost their ability to coordinate their muscles, or control their breathing, or perform certain cognitive functions. These results provided early, but valuable, insights into how the brain keeps us alive.

From the Industrial Revolution until the adoption of the first brain imaging technologies by the medical community in the 1940s and ‘50s, these classical observations represented that main body of the neurological literature, and was all that doctors had to go on.

Now imagine the year is 1916 and you’re a military doctor. You have a soldier who has just survived an explosion resulting in a sharp blow to the head. The victim was knocked out for a while, but recovered—except now that he is awake, the soldier has some trouble writing and using a fork to eat.

How do you diagnose this behavior? Remember, you don’t have brain imaging tools. You can’t just take a picture of your patient’s brain and say, I’m sorry, but it looks like your cerebellum is damaged, and that’s why you’re having trouble writing, but here’s what we can do.

To do your work you’ve got to rely on previous research, mostly on animals like Flourens’s rabbits and pigeons, to inform your diagnosis. Therefore, if you want to understand what area of a soldier’s brain might be damaged to cause him to no longer know how to use everyday objects like a toothbrush, you have to combine a keen investigative wit with an extensive knowledge of the previous neurological literature, all with much less technology than what we have today. We are very much in the same boat when it comes to understanding what has happened to zombie brains. Since we can’t get our hands on a real-life zombie to throw into an MRI scanner, we’ll have to resort to this classic method of diagnosis by observation. Our first step on this journey to diagnosing the zombie brain is to provide a basic roadmap of the brain and its different parts. This will become useful when we try and break down what’s gone wrong in zombie brains.

A VAST BIOLOGICAL COMMUNICATION NETWORK

The brain is the organ that drives all voluntary behavior. It is what gets you out of bed in the morning. It is what allows for you to see a sunset, to smell a rose, to taste chocolate, to kick a soccer ball, and to swing a battle-axe at the head of an oncoming zombie.

Essentially the brain is nothing more